/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineEditor/Public/MoviePipelinePIEExecutor.h
Should it render without any UI elements showing up (such as the rendering progress window)?
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="Movie Render Pipeline") void SetIsRenderingOffscreen ( const bool bInRenderOffscreen )